Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$217.64	9.653%	$238.6488	$238.65	$238.65	$238.60
Purchase #2	$102.88	9.301%	$112.4489	$112.45	$112.45	$112.40
Purchase #3	$188.38	9.180%	$205.6733	$205.67	$205.65	$205.70
Purchase #4	$28.90	10.538%	$31.9455	$31.95	$31.95	$31.90
Purchase #5	$223.98	4.794%	$234.7176	$234.72	$234.70	$234.70
Purchase #6	$138.77	3.699%	$143.9031	$143.90	$143.90	$143.90
Purchase #7	$247.38	3.556%	$256.1768	$256.18	$256.20	$256.20
7 purchase totals =	$1,147.93		$1,223.5140	$1,223.52	$1,223.50	$1,223.40